This invention relates to a tone control of the operational type for the purpose of attenuating or emphasizing the bass and treble responses of audio equipments, and more paticularly to a tone control of the operational type which attenuates or emphasizes bass and treble responses by using a bandpass amplifier or filter directly connected to an audio-frequency amplifier.
The prior art tone controls are generally classified into the CR type as shown in FIG. 1(a) and the NF type as in FIG. 1(b). As is well known in the art, the CR type includes an input signal source 1, bass response controlling elements 3 through 7, treble response controlling elements 8 through 11 and a load resistor 12 and is interposed between input and output terminals. Operation of this circuit arrangement will now be discussed, separately, with respect to treble and bass responses.